% 说明
% 有疑惑的地方, 同样是摘录单词, 使用 yl(yellowlight) 命令
% 摘录段落或句子使用 extract 环境
\section{疑惑之处}
\subsection{重点概念}
\begin{enumerate}
    \item \yl{\href{http://www.nlpr.ia.ac.cn/users/szli/MRF_Book/Chapter_1/node18.html}{smoothness}}: It assumes that physical properties in a neighborhood of space or in an interval of time present some coherence and generally do not change abruptly
    \item \yl{Incomplete}: In mathematics, this type of problem where part of the data is missing is called \textit{incomplete}.
    \item \yl{Ill-posed}: In mathematical terms, the cryo-EM structure determination problem is \textit{ill-posed}
\end{enumerate}

\subsection{拓展概念}
\begin{enumerate}
    \item \yl{The free R-factor in X-ray crystallography} 
\end{enumerate}

\subsection{疑惑之处}
\begin{extract}
    By limiting the power of the reconstruction at those frequencies where the signal-to-noise ratio (SNR) is low, these filters impose smoothness on the reconstructed density in real space.
\end{extract}
不太理解这句活, 此处``power''能否理解为``功率''的意思?还是说此处的``power''是一个专业词汇?
